usb: host: introduce usbh_class with init functions

Add functions to register all classes as part of a new usbh_class.c and
a matching usbh_class.h. These functions are called from the function
usbh_init_device_intl() in usbh_core.c to initialize every class upon
connection of a device. The class instances are registered and connected
together as a linked list.

Co-authored-by: Aiden Hu <[email protected]>
Signed-off-by: Josuah Demangeon <[email protected]>

Author: Josuah Demangeon

include/zephyr/usb/usbh.h

@@ -135,10 +135,35 @@ struct usbh_class_data {
 };
 
 /**
+ * @cond INTERNAL_HIDDEN
  */
-#define USBH_DEFINE_CLASS(name) \
-	static STRUCT_SECTION_ITERABLE(usbh_class_data, name)
+struct usbh_class_node {
+	/** System linked list node for registered classes */
+	sys_snode_t node;
+	/** Node information for the slist. */
+	struct usbh_class_data *const c_data;
+};
+/* @endcond */
 
+/**
+ * @brief Define USB host support class data
+ *
+ * Macro defines class (function) data, as well as corresponding node
+ * structures used internally by the stack.
+ *
+ * @param class_name[in]   Class name
+ * @param class_api[in]    Pointer to struct usbh_class_api
+ * @param class_priv[in]   Class private data
+ */
+#define USBH_DEFINE_CLASS(class_name, class_api, class_priv)			\
+	static const struct usbh_class_data class_data_##class_name = {		\
+		.name = STRINGIFY(class_name),					\
+		.api = class_api,						\
+		.priv = class_priv,						\
+	};									\
+	static STRUCT_SECTION_ITERABLE(usbh_class_node, class_name) = {		\
+		.c_data = &class_data_##class_name,				\
+	};									\
 
 /**
  * @brief Initialize the USB host support;

subsys/usb/host/CMakeLists.txt

@@ -5,9 +5,10 @@ zephyr_library()
 zephyr_library_include_directories(${CMAKE_CURRENT_SOURCE_DIR})
 
 zephyr_library_sources(
+	usbh_api.c
 	usbh_ch9.c
+	usbh_class.c
 	usbh_core.c
-	usbh_api.c
 	usbh_device.c
 )
 

subsys/usb/host/usbh_class.h

@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2025 Nordic Semiconductor ASA
+ * Copyright 2025 NXP
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef ZEPHYR_INCLUDE_USBD_CLASS_H
+#define ZEPHYR_INCLUDE_USBD_CLASS_H
+
+#include <zephyr/usb/usbh.h>
+
+/**
+ * @brief Auto-register all compile-time defined class drivers
+ */
+int usbh_register_all_classes(struct usbh_context *uhs_ctx);
+
+/**
+ * @brief Initialize registered class drivers
+ */
+int usbh_init_registered_classes(struct usbh_context *uhs_ctx);
+
+#endif /* ZEPHYR_INCLUDE_USBD_CLASS_H */

subsys/usb/host/usbh_core.c

@@ -10,9 +10,11 @@
 #include <zephyr/devicetree.h>
 #include <zephyr/init.h>
 #include <zephyr/sys/iterable_sections.h>
+#include <zephyr/usb/usbh.h>
 
 #include "usbh_internal.h"
 #include "usbh_device.h"
+#include "usbh_class.h"
 
 #include <zephyr/logging/log.h>
 LOG_MODULE_REGISTER(uhs, CONFIG_USBH_LOG_LEVEL);
@@ -193,13 +195,18 @@ int usbh_init_device_intl(struct usbh_context *const uhs_ctx)
 	}
 
 	sys_dlist_init(&uhs_ctx->udevs);
+	sys_slist_init(&uhs_ctx->class_list);
 
-	STRUCT_SECTION_FOREACH(usbh_class_data, cdata) {
-		/*
-		 * For now, we have not implemented any class drivers,
-		 * so just keep it as placeholder.
-		 */
-		break;
+	ret = usbh_register_all_classes(uhs_ctx);
+	if (ret != 0) {
+		LOG_ERR("Failed to auto-register class instances");
+		return ret;
+	}
+
+	ret = usbh_init_registered_classes(uhs_ctx);
+	if (ret != 0) {
+		LOG_ERR("Failed to initialize all registered class instances");
+		return ret;
 	}
 
 	return 0;